Commit message: flxdec: Don't unref() parent in the chain function

We don't own the reference here, it is owned by the caller and given to
us for the scope of this function. Leftover mistake from 0.10 porting.

https://bugzilla.gnome.org/show_bug.cgi?id=774897
CVE: CVE-2016-9810
CWE: CWE-125
Vulnerability description: The gst_decode_chain_free_internal function in the flxdex decoder in gst-plugins-good in GStreamer before 1.10.2 allows remote attackers to cause a denial of service (invalid memory read and crash) via an invalid file, which triggers an incorrect unref call.

Project: gst-plugins-good
File: gstflxdec.c

gst_flxdec_chain (GstPad * pad, GstObject * parent, GstBuffer * buf)
{
  GstCaps *caps;
  guint avail;
  GstFlowReturn res = GST_FLOW_OK;

  GstFlxDec *flxdec;
  FlxHeader *flxh;

  g_return_val_if_fail (buf != NULL, GST_FLOW_ERROR);
  flxdec = (GstFlxDec *) parent;
  g_return_val_if_fail (flxdec != NULL, GST_FLOW_ERROR);

  gst_adapter_push (flxdec->adapter, buf);
  avail = gst_adapter_available (flxdec->adapter);

  if (flxdec->state == GST_FLXDEC_READ_HEADER) {
    if (avail >= FlxHeaderSize) {
      const guint8 *data = gst_adapter_map (flxdec->adapter, FlxHeaderSize);
      GstCaps *templ;

      memcpy ((gchar *) & flxdec->hdr, data, FlxHeaderSize);
      FLX_HDR_FIX_ENDIANNESS (&(flxdec->hdr));
      gst_adapter_unmap (flxdec->adapter);
      gst_adapter_flush (flxdec->adapter, FlxHeaderSize);

      flxh = &flxdec->hdr;

      /* check header */
      if (flxh->type != FLX_MAGICHDR_FLI &&
          flxh->type != FLX_MAGICHDR_FLC && flxh->type != FLX_MAGICHDR_FLX)
        goto wrong_type;

      GST_LOG ("size      :  %d", flxh->size);
      GST_LOG ("frames    :  %d", flxh->frames);
      GST_LOG ("width     :  %d", flxh->width);
      GST_LOG ("height    :  %d", flxh->height);
      GST_LOG ("depth     :  %d", flxh->depth);
      GST_LOG ("speed     :  %d", flxh->speed);

      flxdec->next_time = 0;

      if (flxh->type == FLX_MAGICHDR_FLI) {
        flxdec->frame_time = JIFFIE * flxh->speed;
      } else if (flxh->speed == 0) {
        flxdec->frame_time = GST_SECOND / 70;
      } else {
        flxdec->frame_time = flxh->speed * GST_MSECOND;
      }

      flxdec->duration = flxh->frames * flxdec->frame_time;
      GST_LOG ("duration   :  %" GST_TIME_FORMAT,
          GST_TIME_ARGS (flxdec->duration));

      templ = gst_pad_get_pad_template_caps (flxdec->srcpad);
      caps = gst_caps_copy (templ);
      gst_caps_unref (templ);
      gst_caps_set_simple (caps,
          "width", G_TYPE_INT, flxh->width,
          "height", G_TYPE_INT, flxh->height,
          "framerate", GST_TYPE_FRACTION, (gint) GST_MSECOND,
          (gint) flxdec->frame_time / 1000, NULL);

      gst_pad_set_caps (flxdec->srcpad, caps);
      gst_caps_unref (caps);

      if (flxh->depth <= 8)
        flxdec->converter =
            flx_colorspace_converter_new (flxh->width, flxh->height);

      if (flxh->type == FLX_MAGICHDR_FLC || flxh->type == FLX_MAGICHDR_FLX) {
        GST_LOG ("(FLC) aspect_dx :  %d", flxh->aspect_dx);
        GST_LOG ("(FLC) aspect_dy :  %d", flxh->aspect_dy);
        GST_LOG ("(FLC) oframe1   :  0x%08x", flxh->oframe1);
        GST_LOG ("(FLC) oframe2   :  0x%08x", flxh->oframe2);
      }

      flxdec->size = ((guint) flxh->width * (guint) flxh->height);

      /* create delta and output frame */
      flxdec->frame_data = g_malloc (flxdec->size);
      flxdec->delta_data = g_malloc (flxdec->size);

      flxdec->state = GST_FLXDEC_PLAYING;
    }
  } else if (flxdec->state == GST_FLXDEC_PLAYING) {
    GstBuffer *out;

    /* while we have enough data in the adapter */
    while (avail >= FlxFrameChunkSize && res == GST_FLOW_OK) {
      FlxFrameChunk flxfh;
      guchar *chunk;
      const guint8 *data;
      GstMapInfo map;

      chunk = NULL;
      data = gst_adapter_map (flxdec->adapter, FlxFrameChunkSize);
      memcpy (&flxfh, data, FlxFrameChunkSize);
      FLX_FRAME_CHUNK_FIX_ENDIANNESS (&flxfh);
      gst_adapter_unmap (flxdec->adapter);

      switch (flxfh.id) {
        case FLX_FRAME_TYPE:
          /* check if we have the complete frame */
          if (avail < flxfh.size)
            goto need_more_data;

          /* flush header */
          gst_adapter_flush (flxdec->adapter, FlxFrameChunkSize);

          chunk = gst_adapter_take (flxdec->adapter,
              flxfh.size - FlxFrameChunkSize);
          FLX_FRAME_TYPE_FIX_ENDIANNESS ((FlxFrameType *) chunk);
          if (((FlxFrameType *) chunk)->chunks == 0)
            break;

          /* create 32 bits output frame */
//          res = gst_pad_alloc_buffer_and_set_caps (flxdec->srcpad,
//              GST_BUFFER_OFFSET_NONE,
//              flxdec->size * 4, GST_PAD_CAPS (flxdec->srcpad), &out);
//          if (res != GST_FLOW_OK)
//            break;

          out = gst_buffer_new_and_alloc (flxdec->size * 4);

          /* decode chunks */
          if (!flx_decode_chunks (flxdec,
                  ((FlxFrameType *) chunk)->chunks,
                  chunk + FlxFrameTypeSize, flxdec->frame_data)) {
            GST_ELEMENT_ERROR (flxdec, STREAM, DECODE,
                ("%s", "Could not decode chunk"), NULL);
            return GST_FLOW_ERROR;
          }

          /* save copy of the current frame for possible delta. */
          memcpy (flxdec->delta_data, flxdec->frame_data, flxdec->size);

          gst_buffer_map (out, &map, GST_MAP_WRITE);
          /* convert current frame. */
          flx_colorspace_convert (flxdec->converter, flxdec->frame_data,
              map.data);
          gst_buffer_unmap (out, &map);

          GST_BUFFER_TIMESTAMP (out) = flxdec->next_time;
          flxdec->next_time += flxdec->frame_time;

          res = gst_pad_push (flxdec->srcpad, out);
          break;
        default:
          /* check if we have the complete frame */
          if (avail < flxfh.size)
            goto need_more_data;

          gst_adapter_flush (flxdec->adapter, flxfh.size);
          break;
      }

      g_free (chunk);

      avail = gst_adapter_available (flxdec->adapter);
    }
  }
need_more_data:
  return res;

  /* ERRORS */
wrong_type:
  {
    GST_ELEMENT_ERROR (flxdec, STREAM, WRONG_TYPE, (NULL),
        ("not a flx file (type %x)", flxh->type));
    gst_object_unref (flxdec);
    return GST_FLOW_ERROR;
  }
}